Aquariums have become increasingly popular as a hobby in recent years, and as individuals become more interested in their hobby, they begin to acquire more expensive and exotic fish for the aquarium. Particularly with respect to many forms of tropical fish, which are attractive when displayed in an aquarium, the fish require heated water in order to simulate the natural environment which they are used to. Moreover, such exotic fish are extremely sensitive to temperature variations and will succumb to fluctuation in temperature of as little as 15.degree. to 20.degree. either above or below their required temperature. As will be appreciated, therefore, many developments have been made in aquarium heaters in order to provide the proper temperature maintenance of the aquarium tank.
One of the difficulties with aquarium heaters is that they sometimes fail at times when the aquarium is not being observed or when the owner happens to be away from home for a period of time. As will be appreciated, even failure for several hours will cause a change in temperature which may destroy an entire tank of expensive tropical fish. Such failures include failure of the metallic parts for controlling the electrical connections to the heater submersed in the tank. As will be appreciated, the areas around aquarium tanks are high in humidity and this high humidity causes oxidation of such metallic parts. In addition, since aquarium heaters are operated by electricity, unless they are properly sealed, accidental dropping of the entire heater including the supporting structure and the control components can cause short circuiting, which is dangerous, not only for the operator of an aquarium, but also for the fish.
Another problem with the control of the temperature in aquariums is the tampering of the heater controls by children or others not knowledgeable in the use of the heater and the problems involved with substantial fluctuations in temperature. That is, a child may move the control knob to a degree causing the heater to raise the temperature of the tank to a level which might cause the destruction of some or all of the fish contained in the tank.
With this invention, by contrast, an aquarium heater is provided with an integral heater control unit connected to and incorporating a sealing cap which provides a moisture barrier seal between the control unit and the glass tube containing the heater element and the connections therefor to the control unit. The sealing cap includes an integral flexible extension surrounding the power cord for the heater and includes the control knob spindle for the heater. The sealing cap is so constructed to engage both the internal and external surfaces of the top of the glass tube of the heater, so as to prevent exposure to moisture for all of the controls and connections of the heater and the heater element.
Combined with the integral sealing cap is a mounting unit which is constructed to surround and form with the sealing cap structure, an assembly which will accommodate the mounting of the heater of the invention universally on any dimension of aquarium wall, including the old type aquarium incorporating a metallic frame and the new type which utilizes only glass walls. Thus, the mounting arrangement of the invention will accommodate a variety of dimensions of aquarium wall. Also, the mounting unit provides an additional seal and cover for the control knob and spindle to protect against the prevailing humidity.
The heater includes a tamper-proof control dial, which is arranged to vary the temperature of the heater only 10.degree. F. in any 180.degree. turn. At that point, the knob engages a stop so that a child turning the knob, for example, can only vary the temperature in the tank 10.degree.. If it is desired to increase the temperature beyond the 10.degree. range of the control knob, it merely has to be lifted from its spindle so that it will pass the stop and be movable to increase or decrease the temperature, as the case may be, an additional 10.degree. for the next 180.degree. turn of the knob.
Other ojects and advantages of the invention will be apparent from the following description, the accompanying drawings, and the appended claims.